xsv map to map columns through regex substitutions

[joshtriplett]

I have a large amount of CSV data, and I'd like to map it through various substitutions to canonicalize it. For instance, "take anything matching this regular expression and map it to this single value". I'd like to provide a list of such regexes (e.g. as a CSV file itself), and do the equivalent of "join" but mapping through regular expressions.

What I would imagine is an xsv map command, very similar in command-line syntax to xsv join (specify a column to map, and another file to map it through), and then XSV would take each entry in that column and attempt to apply each regex to it.

(This could potentially be heavily optimized to check and process the regular expressions in parallel, using something like hyperscan, but for the scale of data I'm working with, I'd also be fine with a linear search through the regexes.)